You can practise rounding numbers to the nearest 10, 100 or 1,000 by using the following website activities. Choose the option that you need to practise or you could challenge yourself by picking the next level.
http://www.topmarks.co.uk/Flash.aspx?f=DartboardRoundingv2
http://www.topmarks.co.uk/Flash.aspx?f=intheboxv2
https://www.topmarks.co.uk/Flash.aspx?f=loopcardsv6
http://www.abcya.com/rounding_numbers.htm
http://www.math-play.com/Rounding-Numbers-Pirate-Game.html
The following site has a helpful explanation for adults who may be helping.